Dry film lubrication



June 7, 1960 D. P. JENSEN ET AL 2,939,309

DRY FILM LUBRMICATION Filed Deo. 7, 1956 United rates Patent DRY FILM` LUBRICAIION Darwin PfJensen, Manhattan Beach, and John R. Jones and John VM. Wilhelm, LosiAngeles, Calif., assignors. to Douglas AircraftCompany, Inc., Santa Monica,r Calif.-

Filed Dec, 7, I956S,er. No; 626,975

23LClaiuz1s.` (Cl. 14th-6.17)

This inventionrelates to dry film lubrication. More particularly, it relates` to a new composition of matter useful for forming a dry solid' lubricant film containing molybdenum disulfide lubricant powder on the surface of `a metallic element subjected in use to mechanical friction andv bondingA the molybdenum disulfide dry lubricant within the film and the film tothe metal surface, relates to they process of forming, such a dry solid lubricant lm onthe lsurfaceof such a metallic eleme11trelatesto` the method for lubricatingthe surface of` such a metallic element `by the application of such a lubricant film thereto with such a composition, and relatesto the articles resulting" from suchprocess having such a dry solidlubricant film jbonded to the surface of the metallic element.

Molybdenum disulfide is known asy a dry solid lubri cant. Various processes have been devised for applying molybdenum disulde in a film to the surface of metal subjected in use to mechanical friction. For` example, molybdenum disulfide has been applied to the metal surface in the form of a film simply by dusting the molybdenum disulfide powder onto the surface. It has beenl applied by spraying or brushing a dispersionvof the powder in a liquid, such as corn syrup, asphalt-base varnish, silicones, glycerine, ethylene glycol,.and polyglycol, and allowing it to dry and cure. Ithas been applied by first phosphating the metallic surface to produce a crystalline layer having a porous surface and then filling-with molyb denurn disulfide powder. Anothermethod ofapplication is by incorporation of the molybdenum disulfide in a resinousY binder followed by application ofV the, mixture .to the surface, which must` bepm-treated for satisfactory results, such as `by phosphatizingsteel, anodizing orv alodining aluminum, acid etching copperor bronze, `Sandblasting stainless steel` surfaces, and then baking the mixture. SomeY of 4such processes4 are described in the publication4 of Climax Molybdenum Company, 500 Fifth Avenue, New` York, entitled Molybdenum Disulfide as a- Lubricant?? andTechnical Note 2628V of the National Advisory Committee for-Aeronautics,entit1ed Bonding of Molybdenum Disulfideto Various Materials-to Form aA Solid Lubricating. Film, I,-theA Bonding Mechanism. None ofvsuch processes of application, however, except -with some resinouspbinders, produces alm which hasfa'satisfactory wear lifeY in use, especially underrheavy loads. This-is particularly revealed as tested by the well-known4 Falex` Machine. Moreoveneveni thosevfilms resulting from the use of af, resinousmaterial which are satisfactory at high loads require a number of steps -for their production; making` theprocess relativelyl uneconomical, especially as compared` with the-simple :processof thisfinvention,n j whichf renders/many of these Steps unnecessary,

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In accordance with our invention, the surprising" andunexpected discovery has been madeA that asatisfactory: dry lubricant film of molybdenum disulfide can be formed. on andr bonded tothe frictional surface of a metallic ele mentrbythevery simpleexpedientofusing only a mixture of a suitable phosphoric.acidfne molybdenum disulu'deA lubricant powder, and solvent; This: mixture containsthephosphoric acidin: solution and molybdenumA disulfide particles in-suspension,and, becauseofthe presenceof the solventisfof such consistence that itv can be sprayedor brushed. onto the-surface ofthe metal. v

In accordance.4 with our invention,A it is` possible. not onlyH to producea lubricantfilm ofmolybdenum disulfide formed on and bondedto metal surfaces substantially as good as or superior tothose produced using the. wellknownresinous binders, but also4 the method in accordance with the'inventionrequires fewer` stepsandmaterials and is simpler and more economical; No special' pre-treat ment, either chemical or4 mechanical, ofthemetalsurface isirequired. The surface,jof.. courseshould be clean. so that the` appliediilm-can contact the metal surface to whichapplied. Moreover, itis. ancspeciallyl important advantage i that, the filmA formedv in.. accordance with the invention is inorganic, will withstand. high. temperatures,- andldoesV notoxidize or otherwise deteriorate orV form unL desirable reaction products.

Accordingly, it is an object of our invention to. provide` a new composition of matter useful'informing `and bond# inga drysolid lubricant flnrof molybdenum. disulfideto the frictional surfaces of metallic. elements.

It is .another object of our invention toprovide a method of bondinga dry solid lubricant film ofk molybdenumadisulfide to the-surface of a metallic elementsubjected, to` mechanical friction during useA in which` theA bonding is effected `by meansV of phosphoric acid..

ltlis stillanother object of. the invention; toprovidev a methodof lubricatingV the surface of fa metallicelement subjected -to mechanicalfrictionin use` by.` applying totthe frictional surface adry solid filmV liibricantofmolybdenum disulfide bondedthereto with phospihorictacid.

A further object of` our invention istheprovision` of metallic elements `the frictional, surfaces. ofwhich carry a `dry film lubricant .of .molybdenum disulfide bonded by means .of.,phosphoric acid.

Other more particular objects, advantages .and uses -ofJ the invention will be apparent from the specification de scribing the invention .taken withzthe accompanying figure,

Thefigureis a plot showingtherelationship of `wear life of films as tested on the-Falex Machine with variations in the composition` of the.relative-proportiousof.thepyrophosphoric acid to-molybdenum` disulfide and of .the phosphorus content inthe phosphoric vacid to molybdenum` di: sulfide. This figureismore particularly. described in con nection With Example 2 below.

In general, the compositions of the inventionare made by'mixing molybdenum disulfide lubricant powder with phosphoric acid dissolved in solvent. Themolybde'num disulfide (MoSz) powder isprefe'rably a dry lubricant powder of `hue particles, `in general :known and used for lubrication;l The phosphoric acids discovered to-be"es' peciallyv suitable for' the invention are;thetpolyrrrerizable" phosphoric acids in Iwhich-the phosphorusispentavalent and bonded to fourA oxygen atoms,J particularly including orthophosphoric lacid (H3PO4) f pyrophosphoric lacid (di:

phosphoric acidaV HP2Oq'),-. andi. triphosphorie acidi (HsPgOi). Theisolventarfor'thezphosphorici-acidsinclude' water, ethyl alcohol, butyl alcohol, normal propanol, ether, dioxane, and benzene.

In carrying out the process of the invention for forming and bonding the dry film lubricant on the metal surface, a liquid film of this composition is applied to the surface of the metal, the solvent is removed by evaporation or drying, and the liquid lm is then cured by air drying or heating, preferably the latter, to set the phosphoric acid, `producing aA relatively hard tenacious film bbnded to the metal surface.

Evidence indicates that the setting of the iilm and bonding tothe metal surface results from (l) a reaction between the metal surface and the phosphoric acid forming metal phosphates lat the metal-film interface to eifect the bonding and (2) a condensation polymerization of the phosphoric acid to effect the setting. This condensation polymerization of the phosphoric acid, which may be augmented by heating, produces a set which holds the MOS-3' particles in the film probably by forming an interlocking structureabout the MoSZ particles. Moreover, the metal phosphates formed at the interface of metal and film are also probably interlocked with the condensation polymers of phosphoric acid.

The cendensation polymerization of phosphoric acid by itself is negligible at room temperature (70 E), even on' a phosphated surface, proceeding more rapidly as the temperature is raised. However, in accordance with the invention, the condensation polymerization takes place in a few hours at room temperature after the composition is applied on the metal surface to be lubricated. At the same time, the composition has a relatively long shelfV life whenrpackaged 4in bottles. These facts sugf gest that there is a complex interaction between the metal phosphates, formed by the action of phosphoric acid on the metal, and the molybdenum disullide, which produces a catalytic action on lthe condensation polymerization of the phosphoric acid.

The reaction of phosphoric acid with the metal should not take place to such an extent or at such a rapid rate, after the liquid coating is applied, as to cause a bubbling and consequent blistering of the film from evolution of too much hydrogen gas. This will, of course, depend on the particular metal and can be controlled for any particular metal, in accordance with the invention, by maintaining the temperature of curing sufficiently low to avoid too much bubbling or by choosing a solvent in which the reactivity of phosphoric acid with the metal is suiciently low to avoid such bubbling, or by a combination of both. For any particular metal and particular solvent, a simple test of applying a small portion of the coating to specimens of the metal and heating to various temperatures will quickly indicate the temperature above which undesirable blistering will result and kthe temperature below which curing should be carried out.

If it is necessary to so lower the temperature that satisfactory curing or polymerization does not take place to produce a film suliciently hard to act as a satisfactory binder for the molybdenum disulfide, a solvent in which the phosphoric acid is less reactive with the metal may be used. The condition of the lilmV may readily be determined by rubbing or scraping with a iknife. if the lilm can be easily removed, the cure or polymerization is not' satisfactory. In accordance with the invention, it has Vbeen discovered that the reactivity of phosphoric acid is greatest` when water is used. as the solvent and that ethyloalcohol and butyl alcohol, in that order, follow waterwith respect -tothe reactivity of phosphoric acid. Combinations of such solvents andY of the other solvents previously mentioned may also be used to obtain a solvent mixture with the desired reactivity Vof the vphosphoric acid forthe particular metal upon which the film is'to be applied and for the desired temperature 'of curing. AThe temperature of curing will usually be within the range of room temperatures of about 70 F. to as high as about 400 vF., but, as pointed out above, should not be so high as to cause the film to blister.

The composition of the invention can be used to provide a lubricated surface on such metals as low carbon steels, alloy steels, corrosion resistant steels, cadmiumplated steels, aluminum alloys, anodized aluminum, magnesium alloys, bronze, copper and titanium. The composition of the invention is particularly useful on cadmium plated steel, producing films with greater load carrying capacity than previously obtained with the commercial products using a resinous binder. The use of the composition of the invention on cadmium-plated steel is more particularly described in Example IV below.

As previously mentioned, the reactivity of phosphoric acid varies with the different metal surfaces involved. With the magnesium alloys, for example, the reaction is rapid and vigorous, and care should be exercised in the manner previously mentioned to prevent excessive blistering of the metal. With the corrosion resistant steels, the reaction proceeds more slowly, and heat is required to complete the curing of the film.

The most satisfactory combinations of temperature and solvent can be ascertained for any particular metal surface by those skilled in the art from the foregoing description and particularly with the simple tests described, taken with the examples below, which illustrate the invention.

The relative proportions of the three essential ingredients, phosphoric acid, solvent, and molybdenum disulfide will in general be determined in accordance with the following considerations. The minimum requirement for the phosphoric acid is that there be enough phosphoric acid to provide a binder for the molybdenum disulfide. There should be a suicient amount of the molybdenum disulfide particles to cover the metal surfaces within the polymerized phosphoric acid binder and form a lubricating coating. On the other hand, the relative amount of the molybdenum disulfide should not be so great as to impair the binding action of the phosphoric acid upon polymerization, resulting in a lilm that will brush or scrape oi too readily. The minimum requirement for the solvent is that there be enough to form a mixture of the phosphoric acid and molybdenum disulfide which can be applied as desired, as by brushing, spraying, or by dipping of the part to be coated'in the mixture. The solvent should not be present in such large amounts as to make the mixture too thin to produce a satisfactory film.

More particularly, in accordance with the invention, it has been found that the longest Wear life of the lubricant lm, as measured by the Falex tester, is obtained when the weight ratio of the phosphoric acid to the molybdenum disulfide or, expressed in other terms, when the weight ratio of the phosphorus content in the phos phoric acid to the molybdenum disulde is within a controlled range. When pyrophosphoric acid is used with the molybdenum disulfide, the longest wear life is obtained when the weight ratio of pyrophosphoric acid to molybdenum disulde is within the range of about 0.06 to 0.6. The optimum results are obtained when the weight ratio of pyrophosphoric acid to molybdenum disulfideis in the range of about 0.15 to 0.5. When these results are expressed as weight ratios of phosphorus content in the phosphoric acid to MoSZ, the preferred range is from about V0.02 to 0.20 withv the optimum results in the `range from about 0.05 to 0,16. These results are more particularly described in Example II below with its accompanying table.- i

As previously mentioned, orthophosphoric acid (H3PO4) may also be used in the composition of the invention. However, --allowance should be made for the greater reactivity of orthophosphoric acid upon the metal surfaces involved. TheV4 use of orthophosphoric acid is more particularlyfdescribed in Example III below. In

act'ditionA toY pyrophosphoric and orthophosphoric acids, triphosphoric acid (H5P3010) may be used. Also, mixturesfofv these phosphoric acids may beA used.

The-thickness-ofthecured'lm is dependent to a large extent upon the method of application of the coating. Films which have been applied by brushing generally have greaterthicknesslthan those which-havebeen applied by spraying. In general, the cured film should not be so thick as to interfere with the function of the lubricated part or so. thin as to presentan ineffective lubricating surface. In accordance wist-h thel invention, it has been found that the preferred thickness of the c u-redfilm is in the range of from 01.0003 to 0.0005. Although longer wear life can be obtained with thicker coatings they are more subject to scuing wear in handling and fitting of the parts prior tor use.

The article in'accordancelvvith'the invention is a metallic element-'with a surface subiect"V to friction in use, which surface is coated with a dry lubricant film made from the compositions described above and bonded to said surfaceby"the4 process described above: The film contains fine molybdenum disulfide dispersed over the surface, and held 'inposition by'fthe polymeriied phosphoric acid and byfthef ractionproducts of the phosphoric; acid with` the metal` surface.

following examples will illustratethe invention:

EXAMPLE I A composition of the invention was made bythoroughly mixing 20 grams" of' finely." powderedl molybdenum disulfide with 5i5 grams of liquid pyrophosphoric acid HiPOq, 100%):` dissolved irr asolvent mixture of' 18 millilitersf of 190'- proof ethyl: alcoholi and 18 milliliters of` normal butanol, forming a suspension of themolybdenum disulfide particles in the pyrophosphoric acid and "alcohol" mixture'. rPhe molybdenum disulfide powder used a commercial grade( of'molybdenum disulfide solid lubricant' groundy ina ha'llmill for 24' hours toa fineness such that 75% ofthe particles Werelessthan l1 microns, 95% offthe particles were less` than 25 microns, and none of` the particles'was largerthan 44 microns (325 mesh). 'Ifhe solvent was used to provide a spraying consistency to the. suspension. The mixture'of. ethanol and butanol gave the desired degree of reactivity of the phosphoric acid the metal` surface on which the composition was applied: and' served to produce the desired hard, resin-like film upon.condensation,polymerization of the phosphoric acidi The composition was sprayed' upon heat-treated (180,000-200,`000 ptsgi'.) 4130 steel Falex parts (blocks and pins) to form a wet film coating thereon. Except for a solvent wipe, the: Faleirj parts were not given any kind of a chemical. or mechanical pretreatment. The appliedtilm was'J dried'. at room` temperature (70 F.) for about minutes andthen cured in a circulatingair oven at 400 F. i1`07 for about 30 minutes. The resulting cured film was. about 0.0005 thick; It' was hard and tough, resisting ordinary wear, and formed an exceedingly slippery lubricating surface.

These FalexA parts carryingI the dry lubricant fihn of the invention were then tested in the Falex Machine under the-severe-conditions of 29.9 revolutions per minute at a gauge load 01"-1-,000 pounds, which corresponds to a unit loadiof about 50,000poi1ndspec square inch. The full `load wasfirst applied` and then the machinerwas started. It; ran fory the. long time of. 150 minutes without incipient failure. A five inch-pound increase in observed frictional torque was. taken in. this,v test as.` the. point of` incipient failure;

The data in TablevIf illustratethe critical ranges for `the `weight ratio` of; the phosphoric acid to molybdenum disulfide forobtaining-the` longest wear life of the cured film. i L i Table l f HPz'Or/M'or P in-HiPzOz/ Falex PyrophosphorlcAtd Gon-l Weight MOS: Weight Wear tent, Grams Ratto Ratio Life,

' Mins:

AllV compositions` shown inY 'Fahle I- were madeV with 20 grams onfolybedenum Vdisulfide using a solvent mixture, as in Example I above, of 18 milliliters 01EA 190 proof ethyl alcohol and 18 milliliters of normal butanol and using the weight ingrams; ofpyrophosphoric acid (H4P2O7)` shown in the table. Each of the compositions was made up, applied' to Falex parts, dried, cured and tested as described in Example I above. Where necessary, a minor proportion of additional solvent mixture was added tot render the liquid suspension readily sprayable. The coating thickness varied from 0.0003" to 0.0005l on all parts.

The results shown in Table I are plotted in Figure 1 of thedrawings. InFi'gure` 1, thewear'life, as measured by the Falexl machine, is-plottedl` against the weight ratio of pyrophosphoric acid to molybdenum `disulfide and also against the Weight ratio-ofphosphorus in the pyrophosphoric acid to molybdenum disulfide. It. will be noted that the longest wear life is obtained when the weight ratioofH4P, O,` to Mosfiswithin` the rangev of 0.06 to 0030iI and? that thev optimum results are obtained when the weight ratio. of HlgOq to M082 is in the range of 0;15- `to0:50. When the results are-expressed as Weight ratios ofi phosphorus` in the phosphoric acid to molybdenum disulfide, the preferred range is from 0.02 to 0.20 with' theoptimum` results inthe range from 0.05 to 0.16.

EXAMPLE III This example illustrates the use' of orthophosphoric acid in thecomposition ofj the invention; The composition was made by thoroughly mixing 20 grams of finely powdered molybdenum disulfide with 8*.5 grams of 85% orthophosphoric acidv percentofHaPO.; andA 15 percent of water) `dissolved i'n3'5 milliliters of normal butanol, forming a suspension of the molybdenum disulfide particles in` the phosphoric acid alcohol solution. The molybdenum disulfide power was the same as for EX- ample I` above.

This suspension was sprayed Iupon heat-treated (180,- 000200,000`p;s.i.)h 4130-steel Falex parts (blocks and pins) to form a wet film coating thereon. This film was dried at room temperature (70" F.) for about 10 minutes and then cured in a circulating air oven at 400 F.i10 F. for about 370 minutes. The resulting film was about 0.0005" thick. It was hard, and tough, resisting ordinary wearand for-med an exceedingly slippery surface.

These Falex parts carrying thisdry solid lubricant film of the invention were thenA tested in the lFalex machine at 299 revolutions per minute at a gauge load of 1000 pounds. Full load was first' applied and then the machine was started. Itranforthe long time of minutes beforeA incipient failure.

EXAMPLE IV in order to demonstrate the superior wear life ofthe composition of the present invention on cadmium-plated steel, the composition described below was prepared and v20% by weight of molybdenum disulfide and about 80% by weight of a phenolic resin binder.

The tests were run on the Falex machine as described in Example I, except that the Falex parts used were made of cadmium-plated 4130 steel heat-treated to 180,- 000 to 200,000 pounds per square inch tensile strength. To improve the wear life of the commercial product, one set of specimens was 'prepared wherein the Falex parts received a chromate pretreatment before application of the lubricant mixture. The results of the tests are shown in Table II.

Table Il Wear Life (Time to Lubricant Coating Pre-Treatment incipient failure) at oi Metal 100# gauge load Commercial Product None-.- 17 minutes. o Chromate 27 minutes. Example IV Composition None. 90 minutes (plus 25` min. at 500i?) At the end of 90 minutes, before the point of incipient failure was reached, the load on the composition of the invention was increased to 500 pounds vgauge and the test continued for 25 minutes more before incipient failure took place.

These comparative tests show that the composition of the invention has outstanding wear life on cadmiumplated steel not only at the load at which the commercial product failed, but also at substantially increased load.

The foregoing describes our invention in its preferred ,aspects and illustrates our invention by way of specific examples, but alteration and modification may be made thereof within the scope of the appended claims without departing from the invention herein disclosed.

We claim:

l. The composition of matter, in the form of a liquid suspension useful for forming a dry lubricant lrn of nely powdered molybdenum disulfide lubricant on the surface of a metallic element subjected in use to mechanical friction, consisting essentially of finely powdered, solid molybdenum disulfide lubricant, polymerizable phosphoric acid the phosphorus of which is pentavalent and bonded to four oxygen atoms, and a solvent for said phosphoric acid, said powdered lubricant being in suspension, and the weight ratio of phosphorus content in the phosphoric acid to the molybdenum disulfide being from 0.02 to 0.20, said solvent being Ipresent in suliicient proportion to provide a liquid suspension which can readily be applied to the surfaces of a metallic element in a thin wet lrn by spraying or brushing but not in great enough proportion so Vthat the composition is too thin to produce a satisfactory film which upon curing forms a dry lubricant film.

2. The composition as defined in claim 1 in which the phosphoric acid is pyrophosphoric acid.

3. The composition as defined in claim l in which the phosphoric acid is 'orthophosphoric acid.

4. The composition as defined in claim l in which the Y phosphoric acid is triphosphoric acid.

5. The composition as defined in claim 1 in which the weight ratio of the phosphorus content in the phosphoric acid to the molybdenum disulfide Vis from 0.05 to 0.16.

l6. The composition as defined in claim 5 in which the phosphoric acid is pyrophosphoric acid.

'7. The composition ofv matter as defined in claim 1 in which said solvent for said phosphoric acid is a'member of the group consisting of water, ethyl alcohol, butyl alcohol, propyl alcohol, ether, dioxane and benzene.V

8. The composition as defined in claim 1 in which said solvent for said phosphoric acid consists of a mixture of solvents.

9. The composition as defined in claim 8 in which said mixture of solvents consists of a mixture of lethyl alcohol and butyl alcohol.

10. A metallic element subject to mechanical friction in use having a dry lubricant film bonded to the surface thereof, said dry lubricant film consisting essentially of a hard film of polymerized phosphoric acid cured toV form a hard film bonded to said surface and having embedded therein a large number of molybdenum disulfide solid lubricant particles covering said surface, the weight ratio of phosphorus contained in the phosphoric acid in said iilm to molybdenum disulfide being from about 0.02 to 0.20.

I11. An element as defined in claim 10 in which said polymerized phosphoric acid is polymerized pyrophosphoric acid.

12. An element as definedin claim 10 in which said .polymerized phosphoric acid is polymerized orthophosphoric acid.

13. An element as defined in claim 10 in which said polymerized phosphoric acid is polymerized triphosphoric acid.

14. A process for forming a molybdenum disulfide dry lubricating film on the surface of a metallic element that is subjected in use to mechanical friction comprising the steps of applying to said metallic surface a film of a liquid coating mixture consisting essentially of polymerizable phosphoric acid in a solvent vehicle with finely divided, solid, molybdenum disulfide lubricant particles uniformly suspended therein, the weight ratio of phosphorus content in the phosphoric acid tothe molybdenum disulfide being from 0.02 to 0.20, drying and curing said `film to polymerize said phosphoric acid and form a substantially hard lm of cured phosphoric acid with said iinely divided, solid, molybdenum disulfide lubricant particles substantially uniformlydistributed within said cured film, said cured film bonded to said metallic surface and said particles bound within the film to thus maintain a lubricating film of molybdenum disulfide dry solid lubricant'on said surface during use when said surface is subjected to mechanical friction.

15. A process as dened in claim 14 in which the phosphoric acid is pyrophosphoric acid.

16. A process as dened in claim 14 in which the phosphoric acid is orthophosphoric acid.

17. A process as defined in claim 14 in which the phosphoric acid is triphosphoric acid.

18. An article as defined in claim 10 in which said film has a thickness of about 0.0003 to 0.0005 inches.

19. The article as defined in claim 10 in which the weight ratio of phosphorus contained in the phosphoric acid in said film to Vmolybdenum disulfide is from about 0.05 to 0.16.

20. A method for lubricating the surface of a metallic element that is subjected in use to mechanical friction,

comprising applying to said surface a film of liquid coating mixture consisting essentially of polymerizable phosphoric acid in a solvent therefor and having uniformly suspended therein finely divided molybdenum disulfide solid lubricant particles, the weight ratio of phosphorus content in the phosphoric acid to the molybdenum disulde being from 0.02 to 0.20, drying and curing said liquid film vto form a hard dry film of cured polymerized phosphoric acid with said finely divided molybdenum disulfide solid lubricant particles uniformly distributed throughout said dry filmysaid dry lm being bonded to said metallic surface and said particles bound within the film to thus maintain a lubricating film of molybdenum disulfide dry solid lubricant on said surface during use when said surface is subjected to mechanical friction.

21. A method as defined in claim 20 in which the phosphoric acid is pyrophosphoric acid. 22 A method as dened in claim in which the phos' 5 4 phoric acid is orthophosphonc acid.

23. A method as dened in claim 2O in which the phosphoric acid is triphosphoric acid. 863,281

References Cited in the fdc of this patent UNITED STATES PATENTS Roland Nov. 7, 1950 Bramberry Dec. 19, 1950 Henricks Mar. 4, 1952 FOREIGN PATENTS Germany Jan. 15, 1953 

1. THE COMPOSITION OF MATTER, IN THE FORM OF A LIQUID SUSPENSION USEFUL FOR FORMING A DRY LUBRICANT ON THE FINELY POWDERED MOLYBDENUM DISULFIDE LUBRICANT ON THE SURFACE OF A METALLIC ELEMENT SUBJECTED IN USE TO MECHANICAL FRICTION, CONSISTING ESSENTIALLY OF FINELY OWDERED, SOLID MOLYBDENUM DISULFIDE LUBRICANT, POLYMERIZABLE PHOSPHORIC ACID THE PHOSPHORUS OF WHICH IS PENTAVALENT AND BONDED TO FOUR OXYGEN ATOMS, AND A SOLVENT FOR SAID PHOSPHORIC ACID, SAID POWDERED LUBRICANT BEING IN SUSPENSION, AND THE WEIGHT RATIO OF PHOSPHORUS CONTENT IN THE PHOSPHORIC ACID TO THE MOLYBDENUM DISULFIDE BEING FROM 0.02 TO 0.20, SAID SOLVENT BEING PRESENT IN SUFFICIENT PROPORTION TO PROVIDE A LIQUID SUSPENSION WHICH CAN READILY BY APPLIED TO THE SURFACES OF A METALLIC ELEMENT IN A THIN WET FILM BY SPRAYING OR BRUSHING BUT NOT IN GREAT ENOUGH PROPORTION SO THAT THE COMPOSITION IS TOO THIN TO PRODUCE A SATISFACTORY FILM WHICH UPON CURING FORMS A DRY LUBRICANT FILM. 